Yes, code G is correct; code G is for *any* direct rollover to or from a traditional account in the 401(k), taxable or not. You performed an In-plan Roth Rollover, which is indeed a (taxable) direct rollover under the tax code.
Code G already by itself indicates that the distribution was rolled over and is therefore not subject to an early-distribution penalty. Code 2 would the the code if this was instead a Roth conversion from a traditional IRA account.
